Copper and/or aluminum based wiring looms have been used for decades to interconnect and provide information transfer between subsystems integrated in aircrafts and other types of vehicles. Wiring looms ageing, resulting from mechanical, electrochemical and thermal stresses, is a known source of system failure. This well-known weakness was proven to be the cause of a number of crashes (such as TWA 800). Moreover, military aircrafts require ballistic impact resilience imposing redundant electrical cablings, following different paths, subsequently adding weight at the expense of payload, as well as complicating maintenance operations. On an aeronautical standpoint, wiring faults are a recurrent cause of unscheduled maintenance, limiting aircraft availability and profitability. Consequently, there is a need to improve vehicle's fault tolerance and ballistic impact resilience and to reduce vehicle's production time and cost.
As EMP (Electromagnetic Pulse) weaponry based on flux compression generators feeding virtual cathode oscillators (or vircators) becomes more common on modern battlefield, RF hardening becomes a hallmark of military vehicles and equipments. High altitude detonation of a nuclear warhead at is another source of EMP which military systems must be protected against. However, the use of metal shielding, dissipative EMP protection and filtering make EMP hardened cablings significantly heavier than conventional wiring. Data lines are the most vulnerable to EMP aggression and Electrostatic Discharges (ESD) as they carry small signals and connect to the most sensitive and fragile components. To some extent, any conventional wiring is a cause of intrinsic electromagnetic weakness both on a radiated emission and radiated susceptibility stand points. Industry's common answer to this problem is to use physically heavier shielded cabling to achieve electromagnetic protection. Given this situation, a further aim of the invention is to significantly reduce the vehicle's vulnerability to EMP aggressions.
Referring to modern electric, or hybrid-electric drive trains, copper and/or aluminum, based wiring is a known weakness, when integrated on aircrafts. Electric drive trains are now being integrated on many UAV and manned aircrafts in the form of small power plant. However, those propulsion systems are usually developed around standard off-shelf components. The usual split configuration includes one or more electric motor(s) powered by one or more separate controller(s) altogether managed by an external control unit. One of the main limitations of those electric propulsion systems resides in their poor electromagnetic compatibility with the surrounding environment: Fast switching power circuitry (such as IGBT and/or MOSFETS) commonly used in motor controller in order to minimize power losses is one cause of electromagnetic compatibility problem. Such circuitry produces high order harmonics, hence significant interference with surrounding avionics and onboard electronic systems. Interferences are generated by controller units in two forms: Radiated Emissions (RE) and/or Conducted Emissions (CE). The former refers to free space propagation of electromagnetic radio waves, whereas the later refers to electromagnetic signals propagating along the power lines and data cables, potentially disturbing the operation of aircraft's systems. Radiated emissions suppression usually requires installing heavy metallic shielding around the controller circuitry, whereas conducted emissions are mitigated by using intrinsically heavy inline filters inserted in the controllers' DC power ports, in combination with shielded cables. Additionally, RF hardening of peripheral avionics and electronics requires a multitude of inline filters to be installed on the inputs/output ports (power supply and data lines) of each avionic system operating in the vicinity of the electric power plant. If those, somewhat heavy, fixes can mitigate the detrimental effect of conducted emissions, they negatively impact system's weight. Given this situation, another aim of the invention is to reduce the vehicle's weight, yet keeping RE and CE interferences under control.
Referring to military systems, industry's usual answer to Electromagnetic Pulse (EMP) and Electrostatic Discharge (ESD) resilience is through the use of multiple optical fibers carrying data communication, deployed in place of conventional copper/aluminum cabling. However, optical fibers and their associated connectors are traditionally quite fragile, require large bending radius and can become heavy when mechanically reinforced to survive battle damages. Another limitation of optical fibers is the inherent susceptibility of the connectors to dust ingress, resulting in difficult maintenance on a Theater of Operations. Considering the high vibration environment found on some military aircrafts, connecting many subsystems in star and spur topologies to the aircraft's flight computer, through a network of multiple conventional optical fibers drastically increases the number of connectors and optical interface and is not a recommended option due to high production cost and statistically reduced reliability. Besides, those systems still suffer from obvious vulnerabilities to ballistic damages as star and spur topologies are intrinsic sources of Single Point Of Failure. Consequently, redundant routes are necessary (in the same manner as with copper wiring) which negatively impacts weight budget. Another aim of the invention is to propose a suitable solution to those current limitations.
In another domain, conventional fly by wire architectures revolving around multiple-redundant centralized computers have become common practice to achieve failure rate compatible with airline standards (exhibiting calculated failure rates as low as 1.10−9 per flight hour). However, those inherently complex and heavy systems are expensive and difficult to transfer to UAV operating on the battlefield. Furthermore, they revolve around inherently centralized computer units suffering from intrinsic ballistic impact weakness. Physically distributing the processing power where it is needed (that is, close to the subsystems being managed) is a solution offering better ballistic impact resilience, although requiring more networking capacity. Such solution revolves around several isolated high speed networks allocated to specific domains (flight controls, engine management, fuel systems, navigation, ECM, ECCM, ISTAR systems). However, conventional wiring suffers from inherent bandwidth limitation, hence limited data speed capability. As high-capacity networking is required in the context of distributed processing, the need for high speed data transmission is stretching data carrying capacity of copper based wiring looms to their limit. Bandwidth limitation of conventional wiring has direct consequence on the backhaul architecture used to interconnect sub-systems: traditionally, star and spurs topologies are the preferred option as they offer the better capacity, but at the expense of fault protection capability. By contrast, ring topologies provide superior fault protection. However, they are difficult to implement in the context of distributed processing due to their inherent bandwidth limitation. Consequently, there is a need to improve distributed intelligence and data carrying capacity, yet not scarifying ballistic resilience.
Patent documents US20040114854 (OUCHI), US20030179978 (IWASAKI), US20100098430 (CHUI), US20020196502 (PERNER) teach us that polymer films can be used to carry light signals in the same manner as an optical waveguide does. In particular, US20040114854 (OUCHI) teaches us that specific optical devices may be used to narrow the emission angle of light signals, for example, to 90 degrees, in order to transmit light signals only to a certain area of the optical waveguide. Those patents address the transmission of light signals through a polymer film; however, none of them provide a solution to network isolation, distributed processing and ballistic impact resilience. In particular, the directional solution disclosed by US20040114854 (OUCHI) increases vulnerability to the effects of ballistic damages.
In general, it would be desirable to have fault tolerant optical apparatus that addresses at least some of the above disadvantages, as well as possibly other issues.